Stopped-flow, flow-flash, and dye-laser photolysis devices have been interfaced to a Super-Nova Mini-computer with 16K of core memory to provide on-line data acquisition, reduction, and analysis. These devices are being used to study the kinetics of ligand-binding for diverse hemoglobins and myoglobins in the ferrous and ferric states. In the ferrous form, binding of CO and 02 is being studied; in the ferric state, ligands are azide cyanide, and fluoride. In nearly all instances the heme-proteins are purified on a preparative scale using isoelectric focusing in gels. We are particularly interested in elucidating the mechanisms by which the protein modifies the reactivity of the iron atom in the heme. Work in progress on the pure components of whale myoglobin rules out long-range electro static interactions as being of significance. Detailed kinetic studies are being carried out on co-operative and non-co-operative dimeric hemoglobins and myoglobins for numerous invertebrates and on the highly-aggregated annelid hemoglobins under varying conditions of pH, temperature, and protein concentration.